Semiconductor memory devices such as dynamic random access memory (DRAM) devices are widely used to store data in computers and electronic products. A DRAM device typically has a large number of memory cells to store the data. The memory cells are typically arranged in rows and columns.
To ensure the reliability of the memory device, each of the memory cells is tested to determine its performance or to detect a defective cell. Typically, to repair a column having a defective cell, the entire column must be replaced by a spare column or redundant column within the memory device. The redundant column has the same number of cells as that of the column having the defective cell. This method for the repair of a column of a memory device is not cost effective or efficient, since not only the defective cell with the column is replaced but good cells within the same column are also replaced. Also, providing an entire redundant column consumes valuable space in the memory device.
Thus, there is a need for a better method to repair a column having a defective cell.